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(NdModeL) E. T. PLATT. BRUSH FOR DYNAMO ELECTRIC MAUHINES.

Patented Dec. 11,1894.

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EDWARD T. PLATT, OF CHICAGO, ILLINOIS, ASSIGNOR OF TVVO-THIRDS TO WILLIAM FREISE AND CHARLES O. MOYER, OF SAME PLACE.

BRUSH FOR DYNAMO-ELECTRIC MACHINES.

SPECIFICATION forming part of Letters Patent No. 530,717, dated December 11, 1 894.

Application filed June 11, 1894- T on whom it may concern:

Be it known that I, EDWARD T. PLATT, of Chicago, Illinois, have invented certain new and useful Improvements in Dynamos, of

which the following is a specification.

My invention relates more particularly to that portion of the dynamo or motor known as the commutator brush, and has for its object the providing of a simple, economical to and efficient commutator brush; and the invention consists in the features and combinations hereinafter described and claimed.

In the drawings, Figure 1 is an end elevation showing an armature shaft and commu- I 5 tator with my improved brushes applied in position for use; Fig. 2, an enlarged sectional elevation of a portion of the commutator and brush; Fig. 3, an enlarged plan view of a portion of the commutator brush, looking at it from the bottom; and Fig. 4, an enlarged sectional detail of one of the contact pieces, taken on line i of Fig. 2, looking in the direction of the arrow.

It is well known in the art of generating 2 5 electrical energy-and particularly with regard to dynamos where the ordinary brush is used for receiving the electrical energy from the commutator, and when such brushes are made, as they usually are, of copper strips 0 contacting the commutator in a flexible mannor-that during the rotation of the dynamo, especially at high rates of speed, the contacting surfaces of the commutator and brush become dry and wear the segments flat, leaving 5 them high on either side of the insulation. This causes the brush to dance during the rotation of the commutator which has become out of true, and forms an are each time the brush leaves the commutator, creating a tend- 0 ency to fuse the brush and draw portions of it out while in a molten state, so that minute particles of copper separate from one segment over the insulation to the other, causing shortcircuiting. The commutator also becoming 5 rough from such use or abuse will deteriorate the contact between the brush and commutator, which results in sparking, thus tending to excessive heat. To prevent such a condition, oil, and-in some cases-compounds of 5c wax, paraffine and plumbago are used, which Serial No. 514,143. (No model.)

not only gums the surface of the commutator but results in preventing a perfect contact between the brush and commutator, and also causes sparking.

To remedy the above objections, and provide a simple, economical commutator brush is the principal object of my invention.

In using my improvement with a dynamo having a commutator, A, made and formed in the usual sections, a, I provide a brush hav- 6o ing a flexible body portion, B, inserted in the usual socket, C, by set screws, and which hasas is usual in such instances--a binding post,

D, to which is secured the wire, d. To form the contact between the body portion of the commutator brush and the commutator, I provide the end, I), of the brush with roller contactin g pieces, E, preferably formed of copper, and arranged on an arc of a circle so as to contact two or more segments of the commutator 7 and prevent sparking, which are provided with pivots, e, rotatably mounted in the portions, G, of the commutator brush. These rolls are secured to the body portion preferably by means of the screws, g. These contact pieces are preferably formed, as above stated, of copper, and have their pivotal portions made by driving through a central axial opening the hardened steel pins or pivots, e. The side pieces, G, are preferably formed of very hard brass, while the flexible body portion of the brush is made of copper so as to ofier as little resistance as possible to the electric current as it is received by the brush and transmitted to the wires. 3

By making the pivots of the contact pieces of hardened steel wire, and the portion forming the bearings of hard brass, it permits a very high number of revolutions to be given to such pieces before the pivots will become heated, and also permits such pieces to revolve at high rates of speed with very little lubrication.

The advantages due to the use of my mechanism are, that the roller pieces of the brush 9 5 are constantly making and breaking contact with the commutator in a rotatable manner, so that there is no sliding connection whatever between the two, doing away with the necessity for lubricating and overcoming the loo trouble of sparking, thereby obtaining a greater efficiency from the generator; for it is well known that where sparking results in the contact between the brush and the commutator formed in the making of an are-- which causes the sparking-there is always oifered some resistance which, in the majority of instances, is detrimental and impairs the efficiency of the machine.

I claim 1. In combination with a dynamo or other 20 per rolls having hardened steel pivots, and

bearing portions for such pivots made of brass and secured to the body portion of the brush, substantially as described.

3. In combination with a dynamo or other electric machine, a commutator brush pro- .vided with a flexible body portion, a contacting portion formed of a series of copper rolls having hardened steel pivots, and brass bearing portions for such roll pivots secured to the body portion, of the brush, substantially as described.

4-. In combination with a dynamo or other electric machine having a commutator, a com mutator brush provided with a flexible body portion, and a series of at least four rolls arranged on an arc of a circle to contact at least two segments of the commutator, substantially as described.

EDWARD T. PLATT.

Witnesses:

THOMAS F. SHERIDAN, ANNIE 0. COURTENAY. 

